Viscosity reduction of kaolin by hydrothermal treatment

ABSTRACT

A hydrothermal treatment for processing kaolin clay slurries containing from 5 - 60% solids in which the plastic crudes are treated between 200* - 460* C. at pressures up to 30,000 pounds pressure per square inch for from 1 - 60 minutes reduces the viscosity of the kaolin slurry at least 20% and often as much as 50 to 90%, producing viscosities on the order of 100 cps at 20 rpm Brookfield or lower. A particularly advantageous embodiment of the present invention is the continuous hydrothermal treatment of kaolin slurries. It has also been found particularly advantageous to employ certain monovalent and divalent cations in the hydrothermal treatment and to utilize somewhat lower temperatures than would be expected in the process of reducing the viscosity of kaolin clays.

[52] U.S. Cl. 432/18, 106/72 [51] Int. Cl. F27b 3/04 [58] Field of Search 263/52, 53 R; 106/72; 432/18 [56] References Cited UNITED STATES PATENTS 3,614,075 l/l97l Hurst 263/52: 3,516,959 6/1970 Jonas 106/72 1969, Pat. No. 3,614,075.

O United States Patent [1 1 [111 3,765,825 Hurst [451 519911151973 VISCOSITY REDUCTION OF KAOLIN BY Primary Examiner-John J. Camby HYDROTHERMAL TREATMENT AtwrneyHarold e s [76] Inventor: Vernon J. Hurst, 445 Westview Drive, Athens, Ga. 30601 [57] ABSTRACT A hydrothermal treatment for processing kaolin clay Nome: The porno of the term of thls slurries containing from 60% solids in which the patent subseqlfem to plastic crudes are treated between 200 460 C. at 1988 has been pressures up to 30,000 pounds pressure per square inch for from 1 60 minutes reduces the viscosity of [22] Ffled' July 1971 the kaolin slurry at least and often as much as [21] Appl. No.: 166,173 to producing viscosities on the order of cps Related U S Application Dam at 20 rpm Brookfield or lower. A particularly advantacontinuafiommp'ar't of Ser No 843 656 y 22 geous embodiment of the present invention is the continuous hydrothermal treatment of kaolin slurries.

It has also been found particularly advantageous to employ certain monovalent and divalent cations in the hydrothermal treatment and to utilize somewhat lower temperatures than would be expected in the process of reducing the viscosity of kaolin clays.

7 Claims, 1 Drawing Figure VISCOSITY REDUCTION OF KAOLIN BY HYDROTHERMAL TREATMENT CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of US. application, Ser. No. 843,656 filed July 22, 1969, now US. Pat. No. 3,614,075.

A co-pcnding application, Ser. No. 843,535, entitled Continuous Hydrothermal Apparatus and Process, filed July 22, 1969, now US. Pat. No. 3,601,378, by the present inventor describes in detail one form of specific apparatus for carrying out the process of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention:

The present invention relates, in general, to hydrothermal reactions and, more particularly, to a particularly advantageous continuous hydrothermal treatment for the reduction of viscosity in kaolin clays.

2. Description of the Prior Art:

Kaolin clay is sold under rigid specifications on properties such as viscosity. Natural variations in the properties of kaolin clays are common as a result in variations in mineral composition, particle size, particle shape, and particle size distribution. Within limits it is possible to alter the properties of kaolin clays by processing techniques such as shear, fractionation, blending, and the use of chemical reagents. Hydrothermal treatment of kaolin clays to alter their properties has received only limited attention as a means of extending the range of useful kaolin materials because the prior art has been limited to batch treatments, characterized by poor control and has produced only limited viscosity reductions. Further, the prior art methods of batch treating have required long times in the heating cycle and, at least, equally long times in the cooling cycle, so that short reaction times for processing were not feasible.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a new, highly effective hydrothermal process for the reduction of kaolin clay viscosity which overcomes the deficiencies of the prior art as described above.

It is a further object of the present invention to provide a hydrothermal process in which the temperature and pressure may be carefully stabilized and controlled.

Another object of the present invention is to provide a process utilizing hydrothermal treatment and processing of slurries without deformation of the kaolin crystals by mechanical forces.

A further object of the present invention is to provide a hydrothermal treatment process in which the kaolin clay slurry is subjected to high temperatures and high pressures for short periods of time in large volumes.

An additional object of the present invention is to provide a hydrothermal treatment process in which a kaolin clay slurry is introduced to, maintained in, and withdrawn from a reaction zone under controlled equilibrium conditions and high pressure with low shear.

Other objects and a fuller understanding of the present invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings.

The present invention in a particularly advantageous embodiment overcomes the deficiencies of the prior artand achieves its objectives by providing for the continuous passage through a central reaction zone for a kaolin clay slurry followed by the introduction of the reacted slurry into one of a plurality of back pressured condenser-exchangers prior to discharge at atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWING In order to facilitate the understanding of the present invention, reference will now be made to the appended drawing of one form of apparatus suitable for carrying out the process of the present invention. The drawing should not be construed as limiting the invention but is exemplary only. In the drawing:

The sole FIGURE is a partial cross-sectional schematic representation of one form of hydrothermal reaction apparatus suitable for carrying out the process of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) A hydrothermal reaction apparatus suitable for carrying out the process of the present invention is shown in the accompanying FIGURE in which generally indicates the central hydrothermal reactor. One of a plurality of condenser-exchangers is indicated at 200 while another condenser-exchanger is indicated at 300.

A high pressure pump 102 serves to feed a slurry through valve 104, passed pressure gauge 106 via tubing 108 into a hydrothermal reaction vessel 110 having a volume of approximately 175 cubic centimeters inside of insulated jacket 112 of the hydrothermal reactor 100.

The hydrothermal reaction vessel 1 10 may be heated by circular end heaters 114 and 116 having a power of 1,000 watts each and by five strip heaters 118 having a power of 500 watts each at the top and by five additional strip heaters 120 having a power of 500 watts each at the bottom.

The temperature of the hydrothermal reaction vessel 110 may be measured by thermocouples 122, 124 and 126 placed as shown in the accompanying figure. The temperature of the hydrothermal reaction vessel 110 may be adjusted in response to the readings of the thermocouples 122, 124, and 126 by adjusting the power applied to each of the heating elements making up 114, 116, 118, and 120.

Tubing 128 serves to transport slurry to either condenser-exchanger 200 through valve 202 or to condenser-exchanger 300 through valve 302.

Tank 130 is provided with circulating water forcooling tubing 128 and valves 202 and 302 by means of inlet 132 and outlet 134.

Condenser-exchanger 200 comprises an inner condenser-exchanger vessel 204 having a volume of approximately 4,360 cubic centimeters. Within the inner condenser-exchanger vessel 204 is a movable plunger 206 which is sealed to the walls of the inner condenserexchanger vessel 204 by rings 208 having the same coefficient of thermal expansion as the walls of the inner condenser-exchanger vessel 204.

Inner condenser-exchanger is water cooled by a flow of water between the walls of water jacket 210 and the outer walls of inner conderser-exchanger vessel 204. The flow of water within the water jacket 210 is maintained by a flow through inlet 212 and out of outlet 214.

A high pressure water pump 216 may be employed to force water through tubing 218 past pressure gauge 220 to produce pressure against the top surface of plunger 206.

A constant inlet pressure needle valve 222 on tubing 218 may be utilized to bleed-off water in the upper portion of condenser-exchanger vessel 204. The flow of the water discharge through water discharge outlet 224 on tubing 218 may be further controlled by valve 226.

The discharge of reacted slurry may be controlled by valve 228 prior to slurry discharge outlet 230.

Tubing 128 also allows for the passage of slurry through valve 302 to condenser-exchanger 300 which also may have a water jacket 304 on the outside of an inner condenser-exchanger vessel 306 having a volume of approximately 245 cubic centimeters.

Within the inner condenser-exchanger vessel 306 is a movable plunger 308 which is sealed to the walls of the inner condenser-exchanger vessel 306 by sealing rings 310 having a like co-efficient of linear expansion to that of the walls of inner condenser'exchanger vessel 306.

A high pressure water pump 312 may be utilized to force water through tubing 314 passed pressure gauge 316 and through valve 318 into the top of inner condenser-exchanger vessel 306 applying pressure to the top of plunger 308.

Water may be bled off through valve 318 and through constant inlet pressure needle valve 320 to water discharge outlet 322.

Reacted slurry may be discharged through valve 324 through the slurry discharge outlet 326.

While specific pumps, tubing, valving thermocouples, gauges, and vessel volumes have been referred to throughout in this description of one form of apparatus suitable for carrying out the present invention it is obvious to one of ordinary skill in the art that many other obvious equivalent means and configurations may be employed. I

The reactor vessels and fixturesare preferably constructed of titanium-aluminum alloys noted for their strength and stability and resistance to corrosion under the operating conditionsof high temperature and pressure. The condenser-exchanger vessels may be made of stainless steel. It is obvious that any suitable: material exhibiting the above described strength, stability and corrosion resistance under the operating conditions of temperature and pressure may be employed. Typical materials illustrating high strength and corrosion resistance under high temperature and pressure operating conditions are various combinations of titanium, aluminum, titanium-aluminum alloys, titanium-aluminum vanadium alloys, waspalloy, and 404 stainless steel.

The control of heat input and of operating pressures may be automatically controlled to the extent desired and warranted by the economics of commercial operations.

In operation, the central hydrothermal reaction vessel 110 is heated by means of end heaters 114 and 116 and strip heaters 118 and 120 while the chamber of the reaction vessel 110 is filled with water from high pressure pump 102 passing through tubing 108 and valve 104. The reactor vessel 110 is brought to operating conditions of temperature and pressure before any further processing on a slurry is begun.

A slurry of clay or other desired material is then pumped into the reaction vessel 110 by the high pressure pump 102, through valve 104. The pressure is monitored by pressure gauge 106 and maintained at a steady value both during the introduction of the slurry and throughout the subsequent processing. The highpressure pump 102 is built so that it maintains a steady pre-set pressure at all times. The slurry is introduced at the top of the reactor vessel 110 while simultaneously withdrawing the water or whatever other material was i in the reactor vessel 110 through valve 202. Note that at this time the valves 104 and 202 are open. The pressure is maintained on the slurry in front of valve 104 by high pressure pump 102.

'During this process water which filled condenserexchanger vessel 204 above plunger 206 is bled off through the needle valve 222 and valve 226. The reaction time is regulated by the rate of bleed-off of the water through needle valve 222. The rate of flow is maintained so that the hot vapors from the reactor vessel 110 are condensed in the tubing 128 surrounded by cold waterin the water tank 130. The rate of flow is adjusted so that the transmit time from the top of reaction vessel to the bottom of reaction vessel is equal to the desired reaction time. For example, a bleed-off rate of 12.3 cubic centimeters per minute will cause the slurry to pass through the reaction vessel 110 with a volume of about 173 cubic centimeters in approximately 14 minutes.

After the reaction vessel 110 has been completely filled with the slurry, by withdrawing the water in a controlled fashion through valve 202, the rate of flow of the slurry through the reactor is thereafter maintained by releasing the water in a controlled fashion from above the plunger 206 in the condenserexchanger vessel204 through needle valve 222. At the start the plunger 206 is close to or at the bottom of the condenser-exchanger 204. As the slurry material passes through the reaction vessel 110 and into the condenserexchanger vessel 204 the plunger 206 moves toward the top of the condenser-exchanger 204.

After condenser-exchanger 204 has been filled to a large extent with slurry, the valve 202 is closed and the valve 302 simultaneously opened. At this point the plunger 308 in condenser-exchanger vessel 306 is at the bottom of the vessel 306. As water is bled off through the needle valve 320, the reacted slurry now enters condenser-exchanger vessel 306.

While condenser-exchanger vessel 306 is being filled, condenser-exchanger vessel 204 can be emptied through valve 228 by pumping water in through the high pressure pump 216 and thereby driving the plunger 206 back to the bottom of the condenserexchanger vessel 204. As soon as condenser-exchanger vessel 204 has been emptied valve 302 may close at the same, time valve 202 is opened. While condenserexchanger vessel 204 is being filled, condenserexchanger vessel 306 can be discharged through valve 324 by pumping in water from high pressure pump 312 through valve 318 to drive the plunger 308 in the condenser-exchanger vessel 306 back down to the bottom of vessel 306.

The above cycling may be repeated as many times as desired and in this manner produce a continuous passage of the slurry through the reactor vessel 110.

The rate of heating around the reactor vessel 110 by elements 114, 116, 118, and 120 can be adjusted to maintain the continuously flowing and reacting slurry at a desired uniform temperature.

The above described apparatus permits a continuous fiow of slurry to be subjected to high temperatures and pressures for any period of time ranging from a couple of minutes to hours.

The above described apparatus has no sharp bends or corners through which the slurry must pass thereby eliminating a major source of blockages and providing for trouble-free continuous operations.

The process of the present invention enables one to introduce suspended clay particles or similar slurried materials under high pressure, to be reacted at a constant high temperature, and to withdraw the slurried material from the reactor and return it to atmospheric pressure without the necessity of passing the slurried materials through such a small orifice as might disrupt the slurried particles mechanically and increase shear on the particles. 1

The process of the present invention is exceptional in that it provides a continuous flow of slurried materials to be subjected to high temperatures and high pressures for controllably short periods of time in large volumes without encountering many of the traditional problems associated with hydrothermal treatments.

While the above description relates to a specific, con tinuous hydrothermal treatment apparatus suitable for carrying out the present invention, other continuous reactors may be employed in which one may have continuous access to and from the reaction vessel by the reactants and products.

It should also be noted that while a continuous hydrothermal reaction is particularly advantageous, the invention of the present case in no way excludes the obvious use of batch processes and apparatus.

Attention is also directed to the fact that it is particularly advantageous to operate the present invention in the defined range below 430 C.

The following examples and tables represent the data obtained in carrying out the process of the present invention; however, it is not intended to limit the scope of the invention to the specifics recited therein.

The Brookfield viscosities are at 70 percent solids unless otherwise noted using a No. l spindle at 20 rpm.

The Hercules viscosities are reported in dyne units at rpm indicated. 18 dyne units is the maximum torque recorded on the viscometer. Higher rpm at 18 dyne units represents lower viscosity.

Unless otherwise noted the hydrothermal treatment pressure was 4,500 5,000 psi.

The hydrothermally treated slurries were in each case flocculated with alum, filtered, and dried in accord with standard viscosity test procedures. Viscosity measurements were made on a chemically dispersed clay system at 70 percent solids with a Brookfield viscometer (Model LVT) at 20 rpm and a Hercules Hi Shear viscometer (Model 24-4AC).

EXAMPLE 1 (Control) A Georgia kaolin clay was tested without hydrothermal treatment to serve as a control for the specified following examples. The unleached brightness of this clay was 82.6 and its leached brightness after treatment with pounds of ZnS,O per ton of dry clay was 84.4. This clay had a Brookfield viscosity of 870 cps and a Hercules viscosity of 18 dynes at 665 rpm.

of Example 1 was hydrothermally treated at 350 for 4 minutes. The unleached brightness of the treated clay was 82.7 and the leached brightness was 84.9. The Brookfield viscosity of the treated clay was 710 and its Hercules viscosity was 18 dynes at 690 rpm. EXAMPLE 3 A 30 percent solids slurry of the clay of Example 1 was hydrothermally treated at 350 C. for 4 minutes to produce a Hercules viscosity of 18 dynes at 700 rpm and a Brookfield viscosity of 580 cps or a reduction of 34.5 percent in Brookfield viscosity. EXAMPLE 4 A 15 percent solids slurry of the clay of Example 1 was hydrothermally treated at 350 C. for 8 minutes to produce a Hercules viscosity of 18 dynes at 755 rpm and a Brookfield viscosity of 530 cps or a reduction of 39 percent in Brookfield viscosity. EXAMPLE 5 A 15 percent solids Georgia kaolin slurry of the clay of Example 1 was hydrothermally treated at 250 C. for l4 minutes. The unleached brightness of the treated clay was 82.7 and its leached brightness was 84.7. The Brookfield viscosity of the treated clay was 740 cps and its Hercules viscosity was 18 dynes at 775 rpm. EXAMPLE 6 A 25 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 250 C. The unleached brightness of this clay following hydrothermal treatment was 80.7 and its leached brightness following additional treatment by 10 pounds of ZnS O per ton of dry clay was 84.4 The Hercules viscosity of the treated clay was 18 dynes at 880 rpm and its Brookfield viscosity was 610 cps for a reduction in Brookfield viscosity of 30 percent. EXAMPLE 7 A 15 percent solids Georgia kaolin slurry of the clay of Example 1 was hydrothermally treated at 300 C. for 14 minutes. The unleached brightness of the treated clay was 80.3 and its leached brightness was 84.3. The Brookfield viscosity of the treated clay was 630 cps and its Hercules viscosity was 18 dynes at 780 rpm. EXAMPLE 8 A 25 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes'at 300 C. The unleached brightness of this clay following hydrothermal treatment was 78.2 and its leached brightness following additional treatment by 10 pounds of ZnS O per ton of dry clay was 84.4 The Hercules viscosity of the hydrothermally treated clay was 18 dynes at 955 rmp and the Brookfield viscosity was 262 for a reduction of Brookfield viscosity of percent.

EXAMPLE 9 A 30 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 300 C.

The unleached brightness of this clay following hydro-v thermal treatment was 75.5 and its leached brightness following the additional treatment by 10 pounds of ZnS O per ton of dry clay was 84.85. The Hercules viscosity of the hydrothermally treated clay was 18 dynes at 910 rmp and the Brookfield viscosity of the hydrothermally treated clay was 336 cps for a reduction in Brookfield viscosity of 61 percent. EXAMPLE l0 4 A 15 percent solids Georgia kaolin slurry of the clay of Example 1 was hydrothermally treated at 350 C. for

14 minutes. The unleached brightness of the treated clay was 78.2 and its leached brightness was 84.5. The Brookfield viscosity of the treated clay was 412 and its Hercules viscosity was 18 dynes at 840 rpm. EXAMPLE 11 A 25 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 350 C. The unleached brightness of this clay following hydrothermal treatment was 74.5 and its leached brightness following additional treatment by pounds of ZnS O per ton of dry clay was 84.3 The Hercules viscosity of the hydrothermally treated clay was 18 dynes at 1,090 rpm and the Brookfield viscosity was 217 cps for a reduction of Brookfield viscosity of 75 percent. EXAMPLE 12 A 30 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 350 C. The unleached brightness of this clay following hydrothermal treatment was 74.75 and its leached brightness following the additional treatment by 10 pounds of ZnS.,O per ton of dry clay was 85.05. The Hercules viscosity of the hydrothermally treated clay was 18 dynes at 1,085 rpm and the Brookfield viscosity of the hydrothermally treated clay was 258 cps for a reduction in Brookfield viscosity of 70 percent. EXAMPLE 13 A 25 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 385 C. The unleached brightness of this clay following hydrothermal treatment was 74.5 and its leached brightness following the additional treatment by 10 pounds of ZnS O per ton of dry clay was 84.5 The Hercules viscosity of the hydrothermally treated clay was 18 dynes at 1,075 rmp and the Brookfield viscosity was 236 cps for a reduction in Brookfield viscosity of 73 percent. EXAMPLE 14 A 30 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 385 C. The unleached brightness of this clay following hydrothermal treatment was 75.05 and its leached brightness following the additional treatment by 10 pounds of ZnS O per ton ofdry clay was 84.75. The Hercules viscosity of the hydrothermally treated clay was 17.0 and the Brookfield viscosity was 236 cps for a reduction in Brookfield viscosity of 73 percent. EXAMPLE 15 A 25 percent solids slurry of the clay of Example 1 was hydrothermally treated for minutes at 300 C. and a pressure of 4,500 psi. The clays unleached brightness after hydrothermal treatment was 74.7 and its leached brightness after treatment with 10 pounds of Zn S 0 per ton of dry clay was 84.4. The treated clay had a Hercules viscosity of l8 dynes at 895 rmp and had a Brookfield viscosity of 290 cps for a reduction of Brookfield viscosity of 67 percent. EXAMPLE 16 A 30 percent solids slurry of the clay of Example 1 rpm and a Brookfield viscosity of 190 cps or a reduction of 78.5 percent in Brookfield viscosity. EXAMPLE 18 A 15 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 430 C. A 70 percent solids slurry of this material showed a Brookfield viscosity of 500 cps and the Hercules viscosity of this 70 percent slurry was 18 dynes at 530 rpm. It should be noted that this measurement represents a 43 percent reduction in viscosity of the slurry. EXAMPLE 19 (Control) A high viscosity crude Georgia kaolin was degritted without dispersant and not further treated prior to testing so as to be a control for the following specified examples. The unleached brightness of this clay was 78.4 and the leached brightness after treatment with 10 pounds of ZnS O per ton was 83.6. The Brookfield viscosity was 945 cps and a Hercules viscosity of 18 dynes at 575 rpm.

EXAMPLE 20 A 25 percent solids slurry of the clay of Example 19 was hydrothermally treated for 8 minutes at 300 C. The unleached brightness of the treated clay was 78.2 and its leached brightness was 83.5. After hydrothermal treatment, the clay had a Hercules viscosity of 18 dynes at 510 rpm and a Brookfield viscosity of 720 cps, a reduction in Brookfield viscosity of 24 percent.

EXAMPLE 21 A 35 percent solids slurry of the clay of Example 19 was hydrothermally treated for 8 minutes at 300 C. The unleached brightness of the treated clay was 78.2 and its leached brightness was 83.4. After hydrothermal treatment the clay had a Hercules viscosity of 18 dynes at 555 rpm and a Brookfield viscosity of 612 cps, a reduction in Brookfield viscosity of 35 percent. EXAMPLE 22 i A 12 percent solids slurry of the clay of Example 19 was hydrothermally treated for 8 minutes at 385 C. The unleached brightness of the treated clay was 76.7 and its leached brightness was 82.0. After hydrothermal treatment the clay had a Hercules viscosity of 18 dynes at 625 rpm and a Brookfield viscosity of 442 cps, a reduction of 53 percent in Brookfield viscosity. EXAMPLE 23 A 23 percent solids slurry of the clay of Example 19 was hydrothermally treated for 8 minutes at 385 C. The unleached brightness of the treated clay was 74.7 and the leached brightness was 81.0. The Brookfield viscosity was 441 cps and the Hercules viscosity was 18 dynes at 650 rpm. This reduction amounts to a 53 percent reduction in Brookfield viscosity.

EXAMPLE 24 A 35 percent solids slurry of the clay of Example 19 was hydrothermally treated for 8 minutes at 385 C. The unleached brightness of the treated clay was 76.7 and the leached brightness was 81.8. The Brookfield viscosity of the treated clay was 590 cps and the Hercules viscosity was 18 dynes at 535 rpm. This hydrothermal treatment resulted in a 38 percent reduction in Brookfield viscosity.

EXAMPLE 25 A 25 percent solids slurry of the clay of Example 19 was hydrothermally treated for 20 minutes at 200 C. at a pressure of 5,000 psi. The clays unleached brightness after treatment was 78.6 and its leached brightness after treatment with 10 pounds of ZnS O per ton as 83.5. The clays Hercules viscosity after treatment was 18 dynes at 585 rpm and the clays Brookfield viscosity after treatment was 740 cps for a reduction of Brookfield viscosity of 22 percent.

EXAMPLE 26 (Control) A degritted crude gray clay was oxidized with NaOCl only. This clay was then filtered and washed, and otherwise untreated to serve as a control for the next example. The minimum Brookfield viscosity of this sample was 714 cps. The clay had an unleached brightness of 80.6 and a leached brightness of 80.9.

EXAMPLE 27 A percent solids slurry of the clay of Example 26 was hydrothermally treated for 8 minutes at 385 C. The minimum Brookfield viscosity was measured as 407 cps for a 43 percent reduction in Brookfield viscosity. The unleached brightness of this clay was 80.3 and the leached brightness was 78.9. No significant brightness loss occurred as a result of the hydrothermal treatment.

EXAMPLE 28 (Control) A plastic crude clay was degritted without dispersant and left otherwise untreated as a control for the next example. The brightness of the unleached portion of this clay was 80.8 and that of the leached portion was 83.2. A 60.0 percent solids slurry of this clay had a Brookfield viscosity of 1,460 cps and a Hercules viscosity of 5.4 dynes.

EXAMPLE 29 A 19 percent solids slurry of the clay of Example 28 was hydrothermally treated for 8 minutes at 385 C. The unleached brightness of the treated clay was 77.5 and the brightness of the leached clay was 83.6. A 60 percent solids slurry of the treated clay produced a 140 cps Brookfield minimum viscosity and a 3.5 Hercules minimum viscosity. A 70 percent solids slurry of the treated clay produced a Brookfield reading of 2,020 cps and a Hercules reading of 18 dynes 450 rpm. The Brookfield viscosity was thus reduced 90 percent. The

. brightness of the feed clay was slightly degraded by hydrothermal treatment, but after leaching, the hydrothermally treated clay was slightly brighter than the leached control. The browning effect of the hydrothermal treatment of this sample was neutralized by leaching, so that the hydrothermal treatment produced no residual discoloration. EXAMPLE 30 (Control) A non-oxidized gray clay, fine fraction, 91.8 percent less than 2 micron particles, was dispersed'with Calgon," filtered and dried to serve as a control for the next example. The unleached brightness of this clay was 74.8 and the leached brightness was 75.1. A 67.0

percent solids slurry had a minimum viscosity of 1,120

a Hercules viscosity of 18 dynes at 200 rpm. While the brightness of the hydrothermally treated clay was degraded slightly the Brookfield viscosity was reduced 37 percent.

EXAMPLE 32 (Control) A Central Georgia kaolin clay was untreated other than for centrifuging, decenting and drying prior to testing so as to serve as a control for the next example. The unleached brightness of this clay was 79.3 and its leached brightness was 85.5 The clays Hercules viscosity was 6.2 and its Brookfield viscosity was 92. EXAMPLE 33 A 30 percent solids slurry of the clay of Example 32 was hydrothermally treated for 30 minutes at 300 C. Following the hydrothermal treatment and prior to testing the slurry was centrifuged, decanted and dried. The unleached brightness of the treated clay was 79.6 and its leached brightness was 85.1. The Hercules viscosity of the treated clay was 7.9 and the Brookfield viscosity was improved 11 percent to 82 cps.

EXAMPLE 34 (Control) A Central Georgia clay was untreated as a control, but was filtered, washed and dried prior to testing. The unleached clay had a brightness of 79.3 and the leached clay had a brightness of 85.5. The clays Hercules viscosity was 6.4 and its Brookfield viscosity was 96. EXAMPLE 35 A 30 percent solids slurry of the clay of Example 34 was hydrothermally treated for 30 minutes at 300 C. The clay was then filtered, washed and dried. The unleached brightness of the treated clay was 79.2 and the leached brightness was 85.0. The Brookfield viscosity of the treated clay was reduced to 95 and the Hercules viscosity of the treated clay was 6.3.

EXAMPLE 36 A 30 percent solids slurry of the high viscosity crude of Example 1 was hydrothermally treated for 8 minutes at 350 C. The resulting percent Brookfield viscosity was 376 cps and the Hercules viscosity was 18 dynes at 745 rpm for a '57 percent reduction in Brookfield viscosity.

EXAMPLE 37 A 30 percent solids slurry of the high viscosity crude of Example 1 was hydrothermally treated for 45 minutes at 350C. The resulting 70 percent Brookfield viscosity was 207 cps and the Hercules viscosity was 18 dynes at 845 rpm for a '77 percent reduction in Brookfield viscosity. I

EXAMPLE 38 v A 30 percent solids slurry of the clay of Example 1 was treated with 0.4% NaOH and hydrothermally treated at 4,800 psi for 14 minutes at 350 C. The 70 percent viscosity figures after treatment were Brookfield 770 cps and Hercules 18 dynes at .765 rpm for a 12 percent change in Brookfield viscosity. EXAMPLE 39 A 25 percent solids slurry of the clay of Example 1 was hydrothermally treated for 14 minutes at 415 C. The 70 percent Brookfield viscosity was 418 and the Hercules 70 percent viscosity was 18 dynes at 850 rpm for a 52 percent reduction in Brookfield viscosity. EXAMPLE 40 A 30 percent solids slurry of fine fraction primary kaolin clay, which prior to treatment had a 66 percent Brookfield viscosity of 380 cps with no flow at 67 percent, had a 304 cps Brookfield viscosity at 67 percent following a hydrothermal treatment at 385 C. for 30 minutes.

All of the above examples were run on the continuous hydrothermal treatment apparatus described above, but similar results'have been obtained on different continuous hydrothermal apparatus and by means The variations in the results of hydrothermal treatof batch processes. ment based upon different clay samples are shown The principle substance of many of the above exambelow in TABLE II. ples grouped by clays is summarized in TABLE I below.

TABLE I HYDROTHERPML I CONDITIONS MINIMUM VISCOSITY TIME TEMP. BROOKFIELD HERCULES BROOKFIELD EXAMPLE Q un) (c.) SOLIDS (CPS) SOLIDS (d ne/r m) 7; REDUCTION 1 -Control 870 70 18/665 2 350 15 710 70 18/690 1 18 3 l .350 30 580 70 18/700 3 4 8 35 5 53 7 /755 39 5 1& 250 15 7A0 70 18/775 15 6 a 1 250 25 610- 70 18/880 30 7 1 300 15 630 70 18/780 28 8 14 300 25 262 70 18/955 70 9 l l 300 30 336 70 18/910 61 10 1 350 412 70 18/8 10 53 11 1 350 25 217 70 18/1090 75 12 14 350 30 258 70 18/1085 71 13 IA 385 25 236 70 18/1075 73 14 1A 385 30 236 70 17.0 73 15 300 290 70 18/895 67 16 300 30 296 70 18/1085 66 17 30 350 30 190 70 18/10 lO 79 18 14 #30 15 500 70 18/530 43 19 Contr-ol 9 18/ 20 8 300 25 720 7O 18 510 2 21 8 300 35 612 70 18/ 55 35 22 8 385 12 M2 70 18 625 53 23 8 385 23 M1 70 18/650 53 2a 8 385 35 59 7 1 35 3 25 20 200 25 7 40 70 18 585 22 26 Control' 71 4 70 27 8 385 15 107 70 1L3 28 C0ntr'ol l l6O 60 5. 1 29 8 385 19 1&0 60 3.5 30 Control 1120 67 18/500 31 8 385 25 700 67 18/815 37 32 -Control 92 70 6.2. 33 30 300 30 82 70 7.9 11 3 -Control 96 TO 6. 4 35 3 3 3 7 -3 l The variations in the results of hydrothermal treatment based upon different clay samples are shown below in TABLE II.

TABLE II BROOKI-IELD EXAMPLE CLAY CONDITIONS CPS UCTION 16 Georgia kaolin 30 min/300C/30j'5 296 66 33 Central Georgia kaolin 3O min/300C/30y$ 82 11 35 Central Georgia kaolin 3O min/300C/30;'$ 95 l The variations in results of hydrothermal treatment based upon different retention times are shown below in TABLE 111.

The variation in results of hydrothermal treatment based upon different temperatures is shown in TABLE TA BLE 1V Brook- Example Temp. Time Solid field Reductron 6 250 14 25 610 30 8 300 14 25 262 70 1 1 350 14 25 217 75 13 385 14 25 236 73 39 4 15 14 25 418 52 5 250 14 15 740 15 7 300 14 15 630 28 10 350 14 15 412 53 9 300 14 30 336 61 1 2 350 14 30 258 70 14 385 14 30 236 73 21 300 8 30 612 35 24 385 8 35 590 38 16 300 30 30 296 66 17 350 30 30 190 78 The variation in results of hydrothermal treatment based upon different solids is shown below in TABLE V.

TABLE V Brook- Example Solids Time Temp. field Rententron A small amount of deflocculant added to the slurry under hydrothermal treatment may be helpful under certain circumstances.

It has also been noted that the addition of sodium hydroxide to the slurry, on the order of one percent or less may be helpful in improving the brightness of the clay, both before and after leaching.

The affects of washing with hot deionized water before hydrothermal treatment, the use of lower temperatures, and the use of certain monovalent and divalent cation additives on the reduction in kaolin clay viscosity produced by the present invention is discussed and illustrated below. EXAMPLE 41 A degritted, spray dried high viscosity Georgia crude was slurried at 25 percent solids with no chemicals added. This sample had an initial Brookfield viscosity of 1,100 cps at percent solids. The charge was washed with hot deionized water prior to hydrothermal treatment. The Brookfield viscosity of the sample immediately prior to hydrothermal treatment was 750 cps at 70 percent solids. The sample was charged to a hydrothermal reactor and treated hydrothermally at 5,000 psi and 340 C for 35 minutes. The resulting Brookfield viscosity of the kaolin clay was 204 cps at 70 percent solids. EXAMPLE 42 A degritted, spray dried high viscosity Georgia crude was slurried at 20 percent solids with no chemicals added. This sample had an initial Brookfield viscosity of 2,900 cps at 70 percent solids. The sample was hydrothermally treated at 390 C and 5,000 psi for 8 minutes. in three successive runs, additives of 56% Al- (OI-1);, 5% Al(OH and 1% KOH were provided in the reactor during the hydrothermal treatment resulting in 70 percent solids Brookfield viscosities after treatment of 484 cps, 422 cps and 420 cps respectively. EXAMPLE 43 The starting clay of EXAMPLE 42 was washed with hot deionized water before hydrothermal treatment. The clay immediately prior to hydrothermal treatment had a 70 percent solids Brookfield viscosity of 970 cps. A 20 percent solids slurry of this clay with 1% KOH and 4% Al(OH added was hydrothermally treated at 340 C and 5,000 psi for 14 minutes producing a reduction in Brookfield viscosity to 134 cps at 70 percentsolids. EXAMPLE 44 The starting clay of EXAMPLE 42 was washed as in EXAMPLE 43. A 20 percent solids slurry of this clay with 2% K011 and 10% Al(OH); added was hydrothermally treated at 340 C and 5,000 psi for 8 minutes. The Brookfield viscosity-of the resulting clay was 178 cps at 70 percent solids following successive filtering to remove excess chemicals.

The presence of unreacted Al(OH), indicates that smaller amounts of additives may be employed than utilized above.

While mechanism of viscosity reduction by hydrothermal treatment is not fully understood in all of its aspects at this time, it is believed desirable to carry out the hydrothermal treatment in the 200-365 C range for pressures up to approximately 20,000 psi and preferably'in the range 200-340 C inclusive at pressures on the order of 5,000 7,000 psi.

The mechanism of cation addition in the hydrothermal treatment, while not fully understood, is believed related to the crystal habit and form and the ionic charge and size of the cations added. Thus, in addition to the beneficial affect on viscosity reduction illustrated above by potassium and aluminum cations, the addition of cations of sodium, rubidium, cesium, magnesium, calcium, strontium, and barium may be expected to produce similar effects.

While the invention has been described with references to its preferred embodiments, it will be understood by those skilled in the art that various changes may be I to the teachings of the invention without departing from the scope of its essential teachings.

What is claimed is:

l. The method of reducing the viscosity of a naturally occurring kaolin clay having a solids content between and 60 percent by a hydrothermal treatment comprising:

a washing said kaolin clay with hot deionized water prior to said hydrothermal treatment,

b. heating said slurry in a reaction zone,

0. retaining said slurry in said reaction zone for a predetermined retention time of from approximately I to 60 minutes,

d. maintaining a temperature greater than 200 C but less than 390 C in said reaction zone, and

2. simultaneously applying a restraining pressure less than 10,000 pounds per square inch sufficient to provide said predetermined retention time for said slurry in said reaction zone.

2. The method of reducing the viscosity of a naturally occurring kaolin clay having a solids content between 5 and 60% by a hydrothermal treatment comprising:

a. heating said slurry in a reaction zone in the presence of cations selected from the group consisting of aluminum, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium ions and combinations thereof,

b. retaining said slurry in said reaction zone for a predetermined retention time of from approximately 1 to 60 minutes,

0. maintaining a temperature greater than 200 C but less than 390 C in said reaction zone, and

d. simultaneously applying a restraining pressure less than 10,000 pounds per square inch sufficient to provide said predetermined retention time for said slurry in said reaction zone.

3. The method of claim 2 wherein said cations are present in amounts of from 0.1 to 15 percent of the slurry treated.

4. The method of claim 3 wherein said cations include up to 15 percent potassium ions.

5. The method of claim 3 wherein said cations include up to 15 percent aluminum ions.

6. The method of claim Bwherein said cations include a combination of potassium and aluminum ions.

7. The method of claim 6 wherein said combination of additives comprises up to 5 percent potassium ions and up to 10 percent aluminum ions.

- l i t F 1K 

2. The method of reducing the viscosity of a naturally occurring kaolin clay having a solids content between 5 and 60% by a hydrothermal treatment comprising: a. heating said slurry in a reaction zone in the presence of cations selected from the group consisting of aluminum, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium ions and combinations thereof, b. retaining said slurry in said reaction zone for a predetermined retention time of from approximately 1 to 60 minutes, c. maintaining a temperature greater than 200* C but less than 390* C in said reaction zone, and d. simultaneously applying a restraining pressure less than 10, 000 pounds per square inch sufficient to provide said predetermined retention time for said slurry in said reaction zone.
 3. The method of claim 2 wherein said cations are present in amounts of from 0.1 to 15 percent of the slurry treated.
 4. The method of claim 3 wherein said cations include up to 15 percent potassium ions.
 5. The method of claim 3 wherein said cations include up to 15 percent aluminum ions.
 6. The method of claim 3 wherein said cations include a combination of potassium and aluminum ions.
 7. The method of claim 6 wherein said combination of additives comprises up to 5 percent potassium ions and up to 10 percent aluminum ions. 